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Conbercept is a genetically engineered homodimeric protein for the treatment of wet age-related macular degeneration (wet AMD) that functions by blocking VEGF-family proteins. Its huge, highly variable architecture makes characterization and development of a functional assay difficult. In this study, the primary structure, number of disulfide linkages and glycosylation state of conbercept were characterized by high-performance liquid chromatography, mass spectrometry, and capillary electrophoresis. Molecular modeling was then applied to obtain the spatial structural model of the conbercept–VEGF-A complex, and to study its inter-atomic interactions and dynamic behavior. This work was incorporated into a platform useful for studying the structure of conbercept and its ligand binding functions.

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Nectarivorous insects generally adopt suction or lapping to extract nectar from flowers and it is believed that each species exhibits one specific feeding pattern. In recent literature, large groups of nectarivores are classified as either ‘suction feeders', imbibing nectar through their proboscis, or ‘lappers', using viscous dipping. Honeybees ( Apis mellifera ) are the well-known lappers by virtue of their hairy tongues. Surprisingly, we found that honeybees also employ active suction when feeding on nectar with low viscosity, defying their classification as lappers. Further experiments showed that suction yielded higher uptake rates when ingesting low-concentration nectar, while lapping resulted in faster uptake when ingesting nectar with higher sugar content. We found that the optimal concentration of suction mode in honeybees coincided with the one calculated for other typical suction feeders. Moreover, we found behavioural flexibility in the drinking mode: a bee is able to switch between lapping and suction when offered different nectar concentrations. Such volitional switching in bees can enhance their feeding capabilities, allowing them to efficiently exploit the variety of concentrations presented in floral nectars, enhancing their adaptability to a wide range of energy sources.

In this paper, from a Hamiltonian point of view, the nonlinear optimal control problems are transformed into nonlinear two-point boundary value problems, and a symplectic adaptive algorithm based on the dual variational principle is proposed for solving the nonlinear two-point boundary value problem. The state and the costate variables within a time interval are approximated by using the Lagrange polynomial and the costate variables at two ends of the time interval are taken as independent variables. Then, based on the dual variational principle, the nonlinear two-point boundary value problems are replaced by a system of nonlinear equations which can preserve the symplectic structure of the nonlinear optimal control problem. Furthermore, the computational efficiency of the proposed symplectic algorithm is improved by using the adaptive multi-level iteration idea. The performance of the proposed algorithm is tested by the problems of Astrodynamics, such as the optimal orbital rendezvous problem and the optimal orbit transfer between halo orbits.

The surface precision of an antenna reflector can be improved using the actuation of piezoelectric materials to obtain a high-performance space antenna. In this study, the active shape control of a reflector with piezoceramic (lead zirconate titanate) actuators assembled on ribs is proposed by theoretical and experimental approaches. A finite element model of the integrated reflector–actuator system is established using piezoelectric constitutive equations and the virtual work’s principle. For a desired shape, a closed-loop iterative shape control method based on the influence coefficient matrix model is developed, which resolves the issue of high-precision shape control of the antenna reflector in the presence of model errors. The shape controller based on the proposed closed-loop shape control method is implemented on a planar hexagonal reflector with 30 lead zirconate titanate actuators. Experimental results demonstrate that the closed-loop control is an effective way to improve the surface precision of the reflector considering uncertainties.